My brother put a Summit 600cfm with vacuum secondaries on his 77 El Camino 350 small block. He is having some trouble getting the carb dialed in just right, so I offered to help by polling the Hooniverse faithful.

His big problem right now is at idle speed: the engine stumbles and tries to stall. He said "anytime I'm driving and accelerate from a stop or near stop." Any ideas?